WAVES OF HEAT AND WAVES OP DEATH. 
189 
body is no exception to tbis rule : a ring that will fit tightly 
on the warm finger will fall off the same finger after exposure 
to cold. The whole of the soft parts shrink, and the vessels 
contract and empty themselves of thew blood. Cold applied 
to the skin in an extreme degree blanches the skin, and 
renders it insensible and bloodless. If we prick it, it does not 
bleed, neither does it feel. In cases where the body altogether 
is exposed to extreme cold this shrinking of the external parts 
is universal : the whole sm*face is pale and insensible ; the 
blood in the small vessels superficially placed is forced inwards 
upon the heart and vessels of the interior organs ; the brain is 
oppressed with blood ; sleep, or coma, as it is technically called, 
follows, and at last life is suspended. 
In exposure to the lowest wave of temperature in this 
country these extreme effects are not commonly developed : 
but minor effects are brought out which are most significant. 
In particular, the effect on the lungs is marked. The capillary 
vessels of the lungs, of that fine network which plays over the 
computed six hundred millions of air vesicles, undergo rapid 
contraction when the cold air enters the lungs ; in proportion as 
such contraction is decisive, the blood that should be brought to 
the air vesicles is cut off and the process of oxidation is thus me- 
chanically as well as chemically suppressed. The same contrac- 
tion is also exerted on the vessels of the skin, driving the blood 
into the interior and better protected organs. Hence the reason 
why on leaving a warm room to enter a cold frosty air there 
is an immediate action of the renal organs from pressure of 
blood on them, and not unfrequently a tendency to diarrhoea 
from temporary congestion of the digestive tract. Three factors 
then are at work whenever the low wave of temperature sur- 
rounds the animal organism : abstraction of heat from the body, 
and beyond what is natural ; arrest of chemical action and of 
combustion; mechanical contraction of the vessels most exposed. 
W e cannot view the extent of these changes in the organic 
life, as induced by the low wave of heat, without seeing at once 
the sweep of mischief which exposure to the wave may effect. It 
exerts an influence on healthy life in the middle-aged man, 
and I know of no disease which it does not influence dis- 
astrously. Is the man healthy, it tends to produce internal 
congestion ; has he a weak point in the vascular system of 
his brain, it renders that point liable to pressure and rupture, 
with apoplexy as the sequence ; is he suffering from bronchial 
disease, and obstruction already in his air passages, here is a 
means by which the evils are doubled ; has he a feeble worn 
heart, it is unable to bear the pressure that is put upon it ; 
has he partial obstruction of the kidney circulation, he is 
threatened with complete obstruction ; is he indifferently fed. 
